Breech loading mortar



Oct. 11, 1949. F. ROSENKRANTZ B REECH LOADING MORTAR s Sheet-Sheet 1 Filed NOV. 6, 1946 Oct. H, 1949. I. F. ROSENKRAN TZ BREECH LOADING MORTAR Filed NOV. 6, 1946 3 Sheets-Sheet 3 k7 ar ue/Wm ISAAC E JEEIEENKFQANTZ,;

Patented Oct. 11, 1949 UNITED STATES PATENT OFFICE BREECH LOADING MORTAR Isaac F. Rosenkrantz, Greenbelt, Md.

Application November 6, 1946, Serial No. 708,045 ,2 Claims. (01. 89-21) (Granted under the act of March 3, 1883, as

amended April'30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon; v

My invention relates to mortars, particularly to a breech loading mechanism for assembly on'the tube of a standard muzzle-loading mortar to convert said mortar to one which may be loaded from the'breech, and be fired b'ymeans of a hammer and spring plunger firing pin.

In the present art, a mortar, particularly one of large caliber, is not adapted for directional or low level fire. A mortar shell is ordinarily fired by dropping the complete round down the barrel or tube of the mortar; A primer in the shell hits the firing pin fixed infthe base of the mortar to fire the round, the round being expelled from the tube by thepre'ssure of the gases from the burning propellant. Thus, a mortar was restricted in firing upon targets where the elevation of the target was less than approximately 40 degrees because the shell would not gain suffi cient momentum during its drop within the mortar tube to drive the firing pin into the primer of the shell. Firing on a target below the level of the mortar tube was, of course, but of question. i For these reasons, and because it was also necessary for the loaders to be, exposed to enemy fire when loading the mortar, muzzle-loading mortars could not be used efiiciently in aircraft, or when mounted on a tank or an armored vehicle.

While my invention is adaptableto all types of mortars operated by drop fire in the manner de-- scribed, it is in the present instance applied to the standard 81 mm. M1 muzzle loading mortar, and takes the place of the present means used for firing the said mortar, comprising a base cap with a spherical connection which is used to secure the tube on the base, and afixed firing pin positioned in the cap. Briefly, my breech loading mechanism for mortars comprises a breech ring internally threaded to receive the mortar tube and externally threaded for engagement with a recoil mechanism, a slotted screw type breechblock ,mounted on a block carrier closed and locked, and restrainingmeans to pre-.

vent a shell falling out; of themortar bore.

- In the illustrated embodiment (Figure 1), the

breech loading mortar is shown mounted on the 2 body of a tank, but it should be understood that this application is exemplary only, and that the breech' loading mechanism of my invention may be applied to muzzle loading mortars of larger or smaller caliber, and that the converted mortar may also be arranged for mounting in aircraft, on any armed or unarmed vehicle, or upon a stationary mount for fixed or transitory emplacement. 7

A principal object of my invention is to provide a breech mechanism for mortars which will permit conversion of a muzzle loading mortar into one which may be loaded and fired from the breech end thereof.

An important object of my invention is to provide the mechanism of the character described which will permit'firing of the mortar upon which it is used by means of a spring firing pin actuated by lever or trigger means.

Another important object of my invention is to provide a breech loading mechanism for mortars which will permit mounting the mortar in which it is employed upon aircraft, a tank, or an armored vehicle, so that the said mortar may be loaded and fired from within said aircraft or vehicle.

A further object of my invention is to provide a breech mechanism for mortars which will include safety means for preventing fire of the mortar while the breech is open or unlocked, will insure safe and proper closing of the breech, and which will retract the firing pin simultaneously with the opening of the breech.

Another object of my invention is to provide a breech mechanism for mortars which will include means for retaining a shell in the breech end of a mortar tube while the breech is open and the mortar tube is at a high angle of elevation, and which will prevent a shell dropping out of the muzzle end of the mortar tube when the said tube is pointed downward below the level of the mortar.

Still another object of my invention is to provide a breech mechanism for mortars which will be easy to load, safe to operate. and accurate in firing; which will have an efiicient obturation system; which will not require special ammunition, and which will be simple to assemble and disassemble to permit cleaning and lubrication of 3 drawings, forming part of the specification, wherein similar numbers are used to designate like parts throughout the specification and drawings.

In the drawings:

Figure 1 is a side elevation of a mortar embodying my invention mounted on the body of a tank,

Figure 21s a vertical section through the-breech mechanism of my invention with the breech closed but held in safe position while unlocked, the hammer being shown in elevation, and. the handle and latch partly in elevation,

Figure 3 is an elevation of the closed and lacked breech, with the hammer in firing position,

Figure 4 is a section taken on the line 4 -4 of Figure 2,

Figure 5 is an elevation of the face of the disassembled breechblock.

Figures 6 and 7 are an elevationof the inner face and a longitudinal section, respectively, of the spindle,

Figures 8 and 9 are rear and side el'evational views; respectively", of the firing pin retaining cap, and,

Figure 10 is a rearelevation of the breech ring.

Referring now tothe drawings, Figure 1 shows a mortar designated generally by the numeral [1 pivotally mounted on the body of a tank t2 for elevation and depression, as indicated in the dottedlines. The mortar H comprises a barrel or tube l3 and the breech assembly of the invention, designated generally by' the numeral M. A ball and socket shield [5 is carried on the tank 12, and suitable recoil mechanism It; is provided to absorb the recoil energy of the mortar I I when fired. Since neither the mounting, housing [5, nor recoil mechanism t6 form any part of the invention, and are all old and known in the art', they are not further described.

The mortar breech assembly M of my invention comprises a breech ring H, a breechblock i3, and the component parts of the firing and safety mechanism which will be described later.

Breech ring H is formed from one piece of alloy steel, with a pivot lug 22 of alloy steel welded on the bottom side thereof to form a pivot bearing for the breechblock assembly; The rear end is interiorly threaded to tightly engage, as at 23, opposed threads provided on the standard 8 mm. muzzle loading mortar tube 13, which has been altered at its breech end, as shown at Hi, toprovide a suitable seat for the obturator system, as will be hereinafter pointed out. The rear end is also exteriorly' threaded, as at 21', to fit the recoil mechanism it. A keyway 2'3 is provided at the right side of the front face to form a keeper for a handle latch as will be later pointed out. The front or breech end has internal interrupted threads 18' for engagement with similar threads on the breechblock for the seating of the said breechblock.

The breechblock I 8 is formed from one piece of alloy steel. It contains the firing mechanism, and is supported on the pivoted carrier bracket which provides a pivot for opening and closing said breechblock. The said bracket 24 is slotted and bored at one end to fit the pivot lug 22 on breech ring l1, and is held in position by a pivot pin 25, aretaining cap 26, and a plunger detent 81. A boss 21 at the other end of bracket 24 takes bearing in the said breechblock, and has a bore 49 for apurpose which will be hereinafter pointed out. Breechblock i8 is arranged with interrupted external threads 28' for engagement with the mating threads 18 in the breech ring l7. It is provided with a longitudinal axial bore 29 to fit boss 2'1, and a communicating coaxial bore 30 of smaller diameter to allow passage therethrough of a spindle 3|. Two V grooves 32 and 33 are provided in the face of the block and form the open and closed positions of a safety latch, as will be hereinaiiter pointed out, the groove 32 also forming a seat for a handle 35 constructed and arranged to engage therein, the said handle being adapted for opening and closing said. breechblock. The handle is held in a positive position by two Allen head screws 36 threaded intc the tapped holes 31 in the face of breechblock [8... Handle 35 is provided with a longitudinal slot 39 to receive a spring pressed latch 38! pivotally connected to said handle by pivot pin 43. Handle 35 and latch 38 are bored adjacent one of their respective ends to provide the opposed bores 40 and 4| in which a compression spring 42 is seated to provide means for retaining the latch in slot 23. The breechblock I8 is held in closed position by said spring latch 38 and can be brought to open position by a onequarter revolution of the handle 35. An Alien head screw 44, threaded into a. tapped hole 45 forms a stop for" the breechblock I'B' when it is opened.

Spindle 31 is formed of one piece of alloy steel, and itis held in position in boss IT and breechblock l8 by means of a nut 46' threaded on one end thereof. A compression spring 41 surrounds an elongated section 48 of said spindle and is positioned in bore 49' of the boss 27'. Opposed keyways 5| and 52' are provided in boss 21 and spindle 3|, respectively, to receive a key 50' to positively hold said spindle 3t and prevent the said spindle taming in said. bore.

The spindle 3i is provided at its other end with an cut-flaring 'mushroom head 53 to engage within the breech end of mortar tube l3. The obturator means incorporated in the breech mechanism for sealing said breech mechanism against the gases of" the burning. propellant is positioned on stem 48. between the tapered rear surface of head 53 and the front face of breechblock W. It comprises a circular steel disc 58, a.- rear slot ring 55, an obturator pad 56 of neoprene or similar resilient material engaged between said disc 54 andv the rear surface of head 53, and a front split ring 5T, the said split rings 55 and 51 and'sai'd obturator pad 55 forming a seal for the seat in the tapered end of mortar tube E3.

The spindle 3i is provided with an axial longitudinal bore 58 of varying diameters to receive a cylindrical firing pin 59 therein for reciprocal movement therethrough. The firing pin 59 is enlarged intermediate itsends to provide a thickened portion 65 adapted for sliding contact with a portion of the bore 58*, and to provide a seat for a compression spring 6I' positioned in said bore and about said firing pin; The forward end 62- of said firing pin is of reduced diameter to permit its passage through an aperture 63in the forward end of the mushroom head 53, and alongitudinal slot H is provided adjacent its rearward end, the rearward end of said slot forming a shouldertl The firing pin 59 and spring 6| are held in position in the bore 58 by means of a retainer cap 64 provided two outstanding cars 65 at its forward end to engage within a portion of the bore 58 and allow reciprocal movement of said cap relative to said bore. Cap 64 also provided at its rearward end with a circumferential flange 6G and an outwardly projecting finger B1. A slot68 is providedin said flange 66''for a' 1111 056 which will hereinafter become apparent? i The hammer '69 isipivotallymounted on the carrier bracket 24 by means of a pivot pin it. The hammer is provided withan enlarged head H in which a contact pin 12 is position'edgsaid pin 12 being adapted to strike'against' the rear end of firing pin 59 when said hammer 59 is suddenly pulled by means of a lanyard 13 attached to an outstanding finger 14 through a hole 15 provided therein. v

The numeral 16 designates-fa" safety latch. to prevent firing the mortar jithe breech is fully closed "and locked. Thet'op' of thelatch'is adapted to position in slot 11 in firing pin 59 to retract said firing pin after firing of the mortar simultaneously with the opening of the breech by pressure against the shoulder 8|, and to prevent the forward end 62 of the firing pin becoming stuck in the small aperture 63 in forward end of spindle 3| because of the corroding effect of the gases in the mortar tube i3. Safety latch 16 is pivotally mounted on a spring-urged bevelheaded pin 18 bearing in the carrier bracket 24 by means of a taper pin 88. A compression spring 19 is provided about the shank of the pin I8- between the beveled head of said pin and a shoulder formed in the bore 80 in which the pin is positioned. Positive vertical position is retained by said safety latch fitting in slot 88 in retaining cap 64. The beveled head of the pin 18 contacts the face of the breechblock at all times,

and engages the V groove 33 in the face of the breechblock for safety and ofi positions. The latch 16 also acts as a stop for the hammer 69 when the breech is closed but unlocked, as is clearly shown in Figure 2.

A spring pressed plunger 8| is positioned in a bore 82 formed jointly in the breech ring I! and lug 22, and is secured in place by means of a locking pin 83 slidable in a groove 84 in said plunger. The said plunger 8| is provided with a chisel'top to permit said plunger to be forced into said bore 82 against the resistance of the spring 85 by the camming action of a shell against the taper of its top while said shell is being inserted into said tube. When said plunger is returned to its original position by the released energy 0f spring 85 it retains said shell in the mortar tube should the breech be open and the tube pointed in a high angle of elevation. A split snap-ring 85' is positioned in an annular undercut 86 formed in the interior surface of the tube l3 adjacent the breech end thereof, to prevent the shell falling from the muzzle of the tube when the said muzzle is depressed below the level of the mortar. The bore riders on the fin plates of the shell bear against said snap-ring and expand said ring in the undercut 86 when the mortar is fired.

In operation, the breechblock is released for withdrawal by a quarter turn of handle 35 after latch 38 has been pressed to release it from its engagement in keyway 23. The latch handle is then in the position indicated in the dotted lines in Figure 3, and may be pulled downward to withdraw breechblock l8 and its component assembly from engagement in the breech ring H. In turning handle 35 the interrupted screw threads of the breech ring and breechblock, respectively, have been disengaged, and the firing pin 59, firing pin retainer 64, and safety latch 15 have moved rearward under the force of the released energies of their respective springs. Safety latch 161s nowin thesafety position indicated in Fig--. ure .2, and acts as a stop for hammer .68." When handle 35 is pulled downward the entire breechblock assemblyis withdrawn from the breech ring. and a newround maybe inserted into the tube. Plunger 8| will hold the new round against falling out of theopen breech if thetube is elevated, while snap-ring prevents the round falling through the-muzzle if the tube is depressed. The engagement of the. beveled head of pin '18 in groove 34, prevents accidental turning of I the breechblock whilethe breech is open. After the handle is lifted to close the breech, it is revolved again one-quarterturn to lock the breech, this locking movement also forcing the firing pin retainer and safety latch inward, and freeing the hammer from the restraint of the safety latch. The mortar is now in firing condition.

A feature of my invention is the ease with which the firing mechanism may be disassembled for cleaning or lubricating, and again assembled. To remove the firing pin, the safety latch 16 is raised as far as possible and turned right or left until it contacts the recessed portion of the carrier bracket 24. The retainer cap 64 is pushed in and rotated one-quarter turn to disengage the ears 65, and then pulled out. The firing pin and its spring may now be pulled out. To reassemble, the spring is placed on the firing pin and inserted in the spindle 31. The retainer cap is then placed on the firin pin, the ears 65 in line with the openings in the spindle, pushed until the cap comes to a stop, turned degrees and pulled outwardly. The firing pin is turned so that the slot 11 is down and parallel with the center line of the breech. The safety latch is pulled upward swinging it into vertical position and deposit in the slot 68 of the retainer cap. Assembly or disassembly of the firin pin can be done in a few seconds time without the use of any tool.

Disassembly and assembly of the entire mortar is equally simple. With the breechblock closed, the spindle nut and spring are removed. With the breech open 90 degrees, the breechblock may be removed from the carrier bracket by pushing in on plunger detent 81 and sliding the cap 26 to one side. Then, the spindle and component parts of the obturator system may be readily withdrawn from the breechblock. The safety latch 16, pin 18 and spring 19 are disconnected and removed by withdrawing taper pin 88. The only tool required is a screw driver, if it is necessary to remove the handle 35. To reassemble, it is necessary only to reverse this process.

I have disclosed the invention in the best construction known to me, but it will nevertheless be understood that this is purely exemplary, and that changes and modifications in the construction, arrangement and combination of parts otherwise than as specifically claimed, and substitution of materials and equipment, mechanical or otherwise, may be made without departing from the spirit of the invention set forth in the appended claims.

Having thus described my invention, I claim:

1. Breech mechanism comprising a breech ring and a rotatable breechblock, firing means associated with said breechblock, a carrier bracket pivotally mounted on said breech ring, a hammer mounted on said bracket, and stop means resiliently mounted on said bracket, said stop means restraining said hammer until said breech mechanism is in fully locked position.

2. Breech mechanism comprising a breech ring 8 "w 01 mm follnwing; ref enences are oi record; inv the file of patient Pit-TENTS Name Date 472E289." (Eanefl; May 3, 1892 5392733 Gerdomi May 21', 1895- 5625M Sfihn'id'er Jime 2,. 1896 6283871]! July 11, 1899. Homstromvetl al. ..July 21, 1903- 2,088C5'03= B'roussard .Ju"1 y 27, 1937 2358;885 EangeretvaL ,July 18, 1944' 2,391,854 I Chandler Jan. 1,: 19.46 2515mm 

